Servo adjustment method and apparatus therefor

Abstract

Response delay error is calculated from an instructed position based on a position of a moving body and a position instruction to detect reversal of a servo motor and to compare response delay error produced in reversal of the servo motor and threshold value. In the case where response delay error is a threshold value or greater, the value of the already determined compensation torque is updated into a value that enables the response delay error to be decreased, and allows the moving body to carry out circular arc complementary feed motion under the same condition to compensate, based on the updated compensation torque, instructed torque for instructing the servo motor when reversal of the servo motor is detected. Compensating the instructed torque and updating the compensation torque is repeated until the response delay error is at the threshold value or less. Thus, a reasonable compensation torque is determined such that response delay error at the time of reversal of the servo motor is minimized.

What is claimed is: 
     
       1. An adjustment method for a servo mechanism of servomotors for driving a first feed shaft and a second feed shaft of a moving body, the method comprising: controlling the servomotor of one of the feed shafts while detecting a position of the moving body so that the moving body follows an instructed position to allow the moving body to move in a circular interpolation feed motion under a condition of a designated circular arc radius and a feed rate;   detecting a reversal of the servomotor in which a direction of motion of the moving body changes;   detecting a torque signal sent to the servomotor at the reversal;   calculating a response error deviated from an instructed position based on the position of the moving body and the instructed position;   setting a compensation torque to a predetermined value for serving as a first reference value for correcting an instructed torque;   setting a threshold value for serving as a second reference value for updating the compensation torque;   comparing the response error produced in the reversal of the servomotor with the threshold value;   updating a value of the determined compensation torque into a value that enables the response error to be decreased in a case where the response error is greater than the threshold value, and allows the moving body to carry out the circular interpolation feed motion in the case where the response error is greater than the threshold value;   compensating, based on the updated compensation torque, the instructed torque which is sent to the servomotor in detecting the reversal of the servomotor to update the compensation torque when the response error is greater than the threshold value; and repeatedly carrying out compensation of the torque and updating the compensation torque until the response error is within the threshold value.   
     
     
       2. The servo adjustment method as set forth in claim 1, further comprising deriving a quadrant protrusion, which corresponds to the response error, from a maximum error with a predetermined time from a moment of a quadrant change. 
     
     
       3. The servo adjustment method as set forth in claim 2, further comprising calculating the threshold value by averaging absolute response errors, excluding quadrant protrusions. 
     
     
       4. The servo adjustment method as set forth in claim 1, further comprising: allowing the moving body to carry out circular interpolation feed motion under the condition of an arbitrary circular arc radius and feed rate;   determining the compensation torque such that the response error is less than the threshold value for the arbitrary circular arc radius and feed rate; and   storing the compensation torque corresponding to the arbitrary circular arc radius and feed rate in a compensation torque table.   
     
     
       5. An adjustment apparatus for a servo mechanism of servomotors for driving a first feed shaft and a second feed shaft of a moving body, the apparatus comprising: first position detecting means for detecting a position of the moving body driven by a servomotor of the first feed shaft;   second position detecting means for detecting a position of the moving body driven by a servomotor of the second feed shaft;   a servo mechanism for controlling the servomotors of the feed shafts while detecting the position of the moving body such that the moving body follows an instructed position to allow the moving body to move in a circular interpolation feed motion under the condition of a designated circular arc radius and feed rate;   means for detecting a reversal of the respective servo motors;   means for calculating a response error deviated from an instructed position based on the detected position of the moving body and the instructed position;   means for comparing the response error produced at the reversal of the servomotor with a predetermined threshold value;   means for compensating, based on a predetermined compensation torque, the instructed torque which is sent to the servomotor to decrease the response error; and   means for updating the value of the already determined compensation torque in a case where the response error is greater than the threshold value, into a value that enables the response error to be decreased.     
     
     
       6. The servo adjustment apparatus as set forth in claim 5, the apparatus further comprising: a biaxial signal synthesizer for synthesizing output signals of the first position detecting means and the second position detecting means, and   means for displaying a motion locus of the moving body based on an output of the biaxial signal synthesizer.   
     
     
       7. The servo adjustment apparatus as set forth in claim 5, wherein the means for compensating the instructed torque determines the compensation torque such that the response error is less than the threshold value and prepares a compensation torque table for storing the compensation torque corresponding to an arbitrary circular arc radius and feed rate.